To show Glbal TCP Parameters:
netsh int tcp show global

1. How to enable and disable TCP Chimney Offload (aka TCP offload) in Windows Server 2008 R2:
netsh int tcp set global chimney=enabled
netsh int tcp set global chimney=disabled

Determine whether TCP Chimney Offload is working, type “netstat –t” the line shows “Offloaded” is with Offloaded feature enabled.

2. How to enable and disable RSS in Windows Server 2008 R2:
netsh int tcp set global rss=enabled

3. Disable TCO Autotuninglevel in Windows Server 2008 R2 for performance gain in iSCSI
netsh interface tcp set global autotuninglevel=disabled

Update Jan-24:

I simple enabled everythingand found there is no difference on Equallogic iSCSI IOMeter performance.

TCP Global Parameters
———————————————-
Receive-Side Scaling State          : enabled
Chimney Offload State               : enabled
NetDMA State                        : enabled
Direct Cache Acess (DCA)            : enabled
Receive Window Auto-Tuning Level    : normal
Add-On Congestion Control Provider  : ctcp
ECN Capability                      : enabled
RFC 1323 Timestamps                 : disabled

ECN is Explicit Congestion Notification and is enabled by default and is a little more complex as it tweaks TCP protocol when sending a SYN and is mostly used by routers and firewalls. Since the default is enabled, I’d just set it to the default and be done with it.

One Response to “Fine Tune Windows Server 2008 R2 TCP setting for Equallogic iSCSI SAN”

1. HappySysadmin says:

   October 20, 2010 at 9:33 pm

   Nice hint. I often forget the power of netsh. And I did not know the new -t switch for netstat.
   Thanks for sharing then!

   Reply